Regulatory T cells in malaria - friend or foe?

T cell-mediated inflammatory immune responses contribute to both the clearance and pathology of malaria infections; the host's ability to down-regulate inflammation once parasitemia is controlled is crucial to avoid immune-mediated pathology but remains poorly understood. Various regulatory populations of T lymphocytes can modulate inflammatory immune responses and there has been considerable recent interest in the potential for regulatory T cells to modify the outcome of both murine and human malaria infections. Here, we review these studies, focussing in particular on recent studies in humans, propose a model by which different regulatory T cell populations might contribute to the control of inflammation at different stages of infection and discuss the implications for the design of safe and effective malaria vaccines. © 2009 Elsevier Ltd. All rights reserved.